Macromonomers are defined as reactive oligomers. They are linear and carry some functional groups, preferably at the chain ends. They are classified into addition polymerizable and condensation polymerizable macromonomers based on the nature of the terminal functional groups. The molecular weight of macromonomers range from 500-50,000 and particularly in the range between 1000 and 25000. The synthesis of macromonomers is described in detail in the literature. [Sivaram, S., J. Scientific and Ind. Res., 56, 1, (1997); Gnanou, Y., Ind. J. Technol., 31; 317, (1993); Corner, T., Adv. Polym. Sci., 62, 95, (1984); Rempp. P. F., Adv. Polym. Sci., 58, 53, (1981)].
Macromonomers are generally produced by ionic living polymerization, group transfer polymerization and free radical polymerization techniques. Of these, the radical routes of producing macromonomers are commercially acceptable, as they do not require rigorous experimental conditions. Also, the number of monomers amenable to free radical polymerization is large. Macromonomers are useful in the production of tailor made graft copolymers and find application as surface active agents, compatibilizers, adhesion promoters, organic coatings, and biomaterials.
Preparation of macromonomers via free radical method and/or by condensation method is known in the prior art. In one such application, U.S. Pat. No. 5,066,759 describes a process for preparing macromonomer with two antagonists functional groups. Herein the macromonomer is produced by the reaction between a diisocyanate and a prepolymer with a carboxyl group at one end and a hydroxyl or amino group at the other end. However the diisocyanate may also react with the carboxyl group and would not yield a macromonomer with a well-defined terminal functionality. Eur. Pat. Appl. 248574 (Chem. Abst. 108:187481w) describes the preparation of carboxy group containing hydrophilic macromonomer. Herein, the functional group is derived from initiator fragments. U.S. Pat. No. 5,254,632 describes a process for producing macromonomer through a transesterification reaction between hydroxyl terminated polyalkylmethacrylate and monomeric ester. U.S. Pat. No. 5,185,421 describes the preparation of fluorinated macromonomer with one or more hydroxyl groups. U.S. Pat. No. 4,818,804 describes the preparation of macromonomers derived from vinyl monomers and mercapto compounds. The polycondensable macromonomer thus obtained contains one or more carboxyl groups, which are attached to primary and secondary carbon atoms. This induces a difference in reactivity of the functional groups and limits the usage of such macromonomer in isocyanate polyaddition or polyesterification reactions.
In prior art, the polycondensable macromonomers with antagonist functional groups are obtained by step growth polymerization that contains ill-defined terminal functional groups. Macromonomers produced through radical transfer reaction contains one or more terminal functional groups with different reactivity and limits its usage in further polymerization reactions.